1. Field of the Invention
This invention directs itself to ambulatory monitoring systems for measuring and storing diagnostic parameters. In particular, this invention directs itself to a modular monitoring system, wherein modular monitoring units can be used either independently of one another, or utilized together with at least one module communicating to another through an optical interface. More in particular, this invention directs itself to a system wherein the patient's ECG waveform is monitored and analyzed to identify particular abnormalities, both the ECG waveform and analysis data being stored in a non-volatile memory. Further, this system is directed to a blood pressure monitoring module for taking measurements responsive to a selectively variable repetition rate, selectively actuated for predetermined time intervals, and at times triggered by the ECG monitoring unit, when both are being utilized. More in particular, this invention pertains to an ambulatory monitoring system wherein each of the monitoring unit modules includes a serial interface for coupling with a personal-type computer to allow the physician to program predetermined parameters, observe measurements in real time, and download measurement data stored in the memory of each of the modules. Further, this invention directs itself to ambulatory monitoring units having means for conserving power to enable the units to operate for over twenty-four hours on battery power. Such power conserving means may take the form of a system to vary the operational speed of the monitoring unit's microprocessor, or alternately shutting down the operation of the unit's microprocessor for predetermined periods of time.
2. Prior Art
Some prior art systems, such as that disclosed in U.S. Pat. Nos. 4,211,238; 4,216,779; and, 4,519,398 are directed to ambulatory monitoring systems for both blood pressure and a patient's ECG. In such systems the ECG signal is continuously monitored and stored in a memory or on a magnetic tape. The blood pressure measurement may be made at particular time intervals, with only a provision for manually initiating a measurement at intermediate times. Such blood pressure measurements are stored with the continuous ECG signal, however, there is no provision for the ECG unit triggering a blood pressure measurement.
In other prior systems, such as that disclosed in U.S. Pat. No. 4,566,463 automatic blood pressure monitoring systems are disclosed which are capable of operating responsive to heartbeat abnormalities. While such systems attempt to detect arrhythmias and generate a control signal for initiating the blood pressure measurement, such systems utilize pressure pulse from the blood pressure cuff as the means to detect arrythmias. Further, these systems are not of modular construction wherein the communication between modules is devoid of cabling, and the problems associated therewith. Still further, such systems lack means for conserving power, which is essential in portable long-term monitoring systems.